| 
   
    Intangible assets are comprised of the following:
    
     
   
   
   
   |   | 
     | 
     | 
     | 
     | 
     | 
     | 
     | 
     | 
     | 
     | 
     | 
     | 
    
   
   |   | 
     | 
   Gross Carrying Amount | 
     | 
     | 
   Accumulated Amortization | 
     | 
     | 
   Net Carrying Amount | 
     | 
    
   
   
   
   | 
    At December 31, 2012 
    | 
     | 
     | 
     | 
     | 
     | 
     | 
     | 
     | 
     | 
     | 
     | 
     | 
    
   
   | 
    Intangibles subject to amortization: 
    | 
     | 
     | 
     | 
     | 
     | 
     | 
     | 
     | 
     | 
     | 
     | 
     | 
    
   
   | 
    Backlog 
    | 
     | 
   $ | 
   170 | 
     | 
     | 
   $ | 
   170 | 
     | 
     | 
   $ | 
   —   | 
     | 
    
   
   | 
    Customer relationships 
    | 
     | 
     | 
   2,700 | 
     | 
     | 
     | 
   367 | 
     | 
     | 
     | 
   2,333 | 
     | 
    
   
   |   | 
     | 
   
      
    | 
   
      
    | 
     | 
     | 
   
      
    | 
   
      
    | 
     | 
     | 
   
      
    | 
   
      
    | 
     | 
    
   
   |   | 
     | 
   $ | 
   2,870 | 
     | 
     | 
   $ | 
   537 | 
     | 
     | 
   $ | 
   2,333 | 
     | 
    
   
   |   | 
     | 
   
      
    | 
   
      
    | 
     | 
     | 
   
      
    | 
   
      
    | 
     | 
     | 
   
      
    | 
   
      
    | 
     | 
    
   
   |   | 
     | 
     | 
     | 
    
   
   | 
    Intangibles not subject to amortization: 
    | 
     | 
     | 
     | 
     | 
     | 
     | 
     | 
     | 
     | 
     | 
     | 
     | 
    
   
   | 
    Permits 
    | 
     | 
   $ | 
   10,300 | 
     | 
     | 
   $ | 
   —   | 
     | 
     | 
   $ | 
   10,300 | 
     | 
    
   
   | 
    Tradename 
    | 
     | 
     | 
   2,500 | 
     | 
     | 
     | 
   —   | 
     | 
     | 
     | 
   2,500 | 
     | 
    
   
   |   | 
     | 
   
      
    | 
   
      
    | 
     | 
     | 
   
      
    | 
   
      
    | 
     | 
     | 
   
      
    | 
   
      
    | 
     | 
    
   
   |   | 
     | 
   $ | 
   12,800 | 
     | 
     | 
   $ | 
   —   | 
     | 
     | 
   $ | 
   12,800 | 
     | 
    
   
   |   | 
     | 
   
      
    | 
   
      
    | 
     | 
     | 
   
      
    | 
   
      
    | 
     | 
     | 
   
      
    | 
   
      
    | 
     | 
    
   
   |   | 
     | 
     | 
     | 
    
   
   | 
    At March 31, 2012 
    | 
     | 
     | 
     | 
     | 
     | 
     | 
     | 
     | 
     | 
     | 
     | 
     | 
    
   
   | 
    Intangibles subject to amortization: 
    | 
     | 
     | 
     | 
     | 
     | 
     | 
     | 
     | 
     | 
     | 
     | 
     | 
    
   
   | 
    Backlog 
    | 
     | 
   $ | 
   170 | 
     | 
     | 
   $ | 
   170 | 
     | 
     | 
   $ | 
   —   | 
     | 
    
   
   | 
    Customer relationships 
    | 
     | 
     | 
   2,700 | 
     | 
     | 
     | 
   232 | 
     | 
     | 
     | 
   2,468 | 
     | 
    
   
   |   | 
     | 
   
      
    | 
   
      
    | 
     | 
     | 
   
      
    | 
   
      
    | 
     | 
     | 
   
      
    | 
   
      
    | 
     | 
    
   
   |   | 
     | 
   $ | 
   2,870 | 
     | 
     | 
   $ | 
   402 | 
     | 
     | 
   $ | 
   2,468 | 
     | 
    
   
   |   | 
     | 
   
      
    | 
   
      
    | 
     | 
     | 
   
      
    | 
   
      
    | 
     | 
     | 
   
      
    | 
   
      
    | 
     | 
    
   
   |   | 
     | 
     | 
     | 
    
   
   | 
    Intangibles not subject to amortization: 
    | 
     | 
     | 
     | 
     | 
     | 
     | 
     | 
     | 
     | 
     | 
     | 
     | 
    
   
   | 
    Permits 
    | 
     | 
   $ | 
   10,300 | 
     | 
     | 
   $ | 
   —   | 
     | 
     | 
   $ | 
   10,300 | 
     | 
    
   
   | 
    Tradename 
    | 
     | 
     | 
   2,500 | 
     | 
     | 
     | 
   —   | 
     | 
     | 
     | 
   2,500 | 
     | 
    
   
   |   | 
     | 
   
      
    | 
   
      
    | 
     | 
     | 
   
      
    | 
   
      
    | 
     | 
     | 
   
      
    | 
   
      
    | 
     | 
    
   
   |   | 
     | 
   $ | 
   12,800 | 
     | 
     | 
   $ | 
   —   | 
     | 
     | 
   $ | 
   12,800 | 
     | 
    
   
   |   | 
     | 
   
      
    | 
   
      
    | 
     | 
     | 
   
      
    | 
   
      
    | 
     | 
     | 
   
      
    | 
   
      
    | 
     | 
    
   
    
 |